Enhancement Effect of C40 TiSi[sub 2] on the C54 Phase Formation

Abstract

We report on the formation of a new material, C40 TiSi 2 , using pulsed laser annealing. On the basis of this laser-induced C40 TiSi 2 , the growth of the technologically important C54 phase is significantly promoted and can be accomplished with a subsequent rapid thermal anneal or furnace annealing at temperatures far below that for the normal C54 formation. The undesirable C49 TiSi 2 is completely bypassed. C40 TiSi 2 can also be easily transformed to the C54 phase with thermal treatments and result in the formation of a pure C54 TiSi 2 layer. The synthesis of C40 phase without the additional refractory metals and its promotion effect on the C54 phase formation have great potential for applications in the integrated circuit industry for 0.10 m technology node and beyond.Titanium disilicide ͑TiSi 2 ) has been widely applied as contact and gate electrodes for complementary metal-oxide-semiconductor ͑CMOS͒ transistor in ultralarge-scale integration ͑ULSI͒ technology. 1 In the current semiconductor industry, rapid thermal annealing ͑RTA͒ is used to fabricate TiSi 2 from Ti/Si wafers. The high resistivity ͑60-70 ⍀ cm͒ metastable C49 phase forms first at RTA temperatures of 550-700°C and transforms to the lowresistivity ͑15-20 ⍀ cm͒ stable C54 phase at higher temperatures of 750-850°C. C54 TiSi 2 is the preferred phase for integrated circuit ͑IC͒ fabrication due to its lower resistivity and better thermal stability as compared with C49 phase. Therefore, a complete C49 to C54 phase transition is important for IC fabrication. However, due to the ''fine line effect'', 1 the transformation to C54 phase on narrow polysilicon lines requires very high annealing temperature, which causes severe problems such as agglomeration 2 and ''punch through'' 3 and results in device failure. Promoting C54 phase formation at low annealing temperatures is essential in terms of both industrial requirements and scientific interests.The conventional preamorphization implantation ͑PAI͒ 4 and implantation through metal ͑ITM͒ 5 methods were usually used to enhance the C54 phase formation by using implantation to create an amorphous Si surface. In recent studies, refractory metals were found to facilitate the C54 phase formation and three approaches were developed to lower the C54 phase formation temperature. A group of IBM researchers first demonstrated that ion implantation of a small dose of refractory metals into the Si substrate prior to Ti deposition could reduce the C54 TiSi 2 formation temperature by 100-150°C. 6 Cabral et al. from the same group later revealed that codeposition of Ti alloyed with refractory metals could serve the same purpose. 7 Mouroux et al. 8 used a different approach in which a thin layer of refractory metal was deposited between Ti capping layer and Si substrate, and the C54 phase was obtained at 100°C lower than the normal C54 formation temperature. 8 Here we demonstrate a different approach to enhance the C54 phase growth and to effectively lower its formation temperature, using laser processing as the first ann...

Impact of nanosecond laser energy density on the C40-TiSi2 formation and C54-TiSi2 transformation temperature

“…The only phase formed after UV-NLA is indeed the C40-TiSi2 whatever the laser ED used. To promote the formation of the C54-TiSi2 phase, an additional RTA is needed in agreement with previous studies [34][35][36]57 .…”

“…5a) show the presence of some silicide crystallites in the silicide layer. Since the C40-TiSi2 is known to be a stoichiometric phase 35,50 as the majority of other C40-TiSi2 structures (WSi2 51 and CrSi2 51,52 , VSi2 53 , TaSi2 54 ), the silicide cannot be only composed of the C40-TiSi2 phase. However, the HRTEM micrograph in Fig.…”

“…Another major interest of the laser annealing process is to modify the phase sequence: indeed the C54-TiSi2 phase can be obtained from C40-TiSi2, by-passing the undesirable C49-TiSi2 phase [34][35][36] . The C40-TiSi2 phase, obtained for very specific conditions, can thus act as a precursor of the C54-TiSi2 at lower temperature [34][35][36] . The This is the author's peer reviewed, accepted manuscript.…”

“…investigation performed so far on leveraging UV-NLA for the formation of TiSi2 have been mainly conducted with small laser beams (diameter ~160-200 µm) with a near Gaussian shape scanning the surface with a controlled speed, resulting in a large number of pulses at the same location (typically more than 100 pulses) [30][31][32][33][34][35][36] . Such studies did not properly explore the effect of the laser energy density.…”

Excimer Laser-Induced Ti Silicidation to Eliminate the Fine-Line Effect for Integrated Circuit Device Fabrication

“…C40 TiSi 2 is also a high resistivity metastable silicide as compared with C54 TiSi 2 . 6 In practical applications, it is very important and necessary to completely convert the metastable high resistivity C40 phase to the stable low resistivity C54 phase, in order to achieve low sheet resistance, low contact resistance, and high process stability. The C40 TiSi 2 will have no advantages over the C49 phase if the C54 phase formation via C40 also suffers from the fine line effect.…”